1. Field of the Invention
The present invention relates to a writing instrument such as a felt pen.
2. Description of the Related Art
Conventionally, writing instruments using a core made of a fabric such as a felt as in a felt pen have been generally such that ink stored in an ink storage chamber is supplied to the pen core by pressing the pen core (see, for example, Japanese Unexamined Patent Publication No. H10-157379.) One example of such writing implements is described with reference to FIG. 4.
A writing implement 100 includes a pen core 5 which is so held in a leading holder 4 provided at the leading end of a pen shaft 3 as to be movable along a longitudinal direction, and a valve 6 movable along the longitudinal direction as the pen core 5 is pressed or freed from a pressed state. The supply of ink from an ink storage chamber 2 to the pen core 5 is controlled by opening and closing an ink flowing passage 10 coupled to the pen core 5 by means of the valve 6.
This pen core 5 is pressed into the leading holder 4 and held therein by a frictional force created by the pressing contact of the outer circumferential surface of the pen core 5 and the inner circumferential surface of the leading holder 4, and a base-end 52 thereof is in contact with the valve 6. Further, the valve 6 is so held as to be movable along the longitudinal direction by a holding member 7, and a pressing spring 8 for biasing the valve 6 toward the leading end of the pen shaft 3 is also held in the holding member 7. The valve 6 is moved in directions toward and away from a valve seat 91 (inner wall of the ink flowing passage 10) to bring a jaw portion 61 into contact with and away from the valve seat 91, thereby opening and closing the ink flowing passage 10. Although not shown, the holding member 7 is formed with an opening to communicate the inside and outside of the holding member 7, and the ink in the ink storage chamber 2 has entered the holding member 7.
In this writing instrument 100, the jaw portion 61 of the valve 6 is separated from the valve seat 91 to open the ink flowing passage 10 and supply the ink to the pen core 5 as shown in FIG. 5 as the pen core 5 is slid along the longitudinal direction upon being pressed. Further, by canceling such a pressed state, the jaw portion 61 of the valve 6 is so moved as to come into contact with the valve seat 91, thereby closing the ink flowing passage 10. Consequently, the pen core 5 is also slid in the leading direction along the longitudinal direction. Thus, a suitable amount of the ink can be supplied to the pen core 5 by pressing the pen core 5 and freeing it from the pressed state.
In this construction, the pen core 5 is held in pressing contact with the inner circumferential surface of the leading holder 4 so as to be securely slidable in order to supply a suitable amount of the ink to the pen core 5.
However, if the pen core 5 is repeatedly slid by being pressed and being freed from the pressed state, a clearance between the pen core 5 and the leading holder 4 is widened by a sectional area of the pen core 5 gradually reduced by a friction or the like occurring between the pen core 5 and the inner circumferential surface of the leading holder 4, and the pen core 5 is made unable to be brought into contact with the leading holder 4 by a reduced frictional resistance between the outer circumferential surface of the pen core 5 and the inner circumferential surface of the leading holder 4 when the pen core 5 absorbs the ink, thereby making the pen core 5 unable to come into pressing contact with the leading holder 4. Therefore, there has been a danger that the pen core 5 comes out of the leading holder 4.
As a method for preventing the pen core 5 from coming out, it can be thought to increase the sectional area of the pen core 5 to hold the outer circumferential surface of the pen core 5 and the inner circumferential surface of the leading holder 4 in pressing contact with a lager force. However, in such a case, a larger force is required to press the pen core 5 into the leading holder 4, thereby hindering a smooth fitting operation of the pen core 5. Further, the pen core 5 may be damaged by a force exerted upon being pressed into the leading holder 4. Even if the pen core 5 is properly pressed into, an excessive press-contact force may hinder a smooth operation.
In other words, quite a strict dimensional control for fitting is required to accomplish both a secure holding of the pen core 5 and smooth movements of the pen core 5 in the conventional writing instrument. It is difficult to carry out such a dimensional control for the pen core made of, e.g. a felt. Thus, productivity is accordingly reduced, thereby raising a problem in reducing production costs.